The vast Wedgwood collection of pottery, art and manuscripts – regarded as one of the most important industrial archives in the world – will be broken up and sold on the open market unless £2.74m can be raised by the end of November.

On Monday the Art Fund announced a three-month fundraising campaign to avert what it said would be a disaster for the nation.

The collection, valued at £15.75m, has been described by the UN cultural organisation, Unesco, as "unparalleled in its diversity and breadth". Most of the money has been found, but not all. Stephen Deuchar, the Art Fund's director, said: "Our worst nightmare is that the collection is dispersed across the world and the threat of that does hang across this appeal very heavily."

Housed in Stoke-on-Trent's Wedgwood museum, the collection consists of more than 8,000 ceramics and 75,000 manuscripts, as well as paintings by artists including George Stubbs and John Singer Sargent.

The future of the museum has been in doubt since Waterford Wedgwood went into administration in 2009.

The demise of the company left a £134m pensions liability and because the museum was still solvent – and five employees were in the pension plan – the rules meant that the full pension debt was transferred to the museum.

The museum trust itself went into administration but that still could not protect the collection. The high court decided in 2011 that it could be sold to repay some of the debt – a ruling upheld by the attorney general in March 2012.

After much legal wrangling, the Art Fund has now come up with a plan it hopes will save the collection for the nation and meet some of the pension liability.

The collection has been valued halfway between Christie's lower and upper valuations of £11m-£22m and if all goes to plan it will be bought by the Art Fund for £15.75m and given to the V&A, which will, in turn, ensure it remains in the Wedgwood museum at Barlaston.

So far £13m has been pledged by the Heritage Lottery Fund and private trusts, leaving £2.74m to be raised by the end of November.

There are questions over why the collection was never properly separated from the company – as was the Wedgwood family's intention in 1961, said a representative, Alison Wedgwood, on Monday.

Tristram Hunt, the historian and Stoke-on-Trent Central MP, said he thought the real villain of the piece was the media tycoon Robert Maxwell. "The consequences of Maxwell's plundering of the Mirror Group pensioners created the pension law, which then had this very unexpected consequence of the 'last man standing' principle."

Deuchar said other collections, partly as a result of what had happened with Wedgwood, had now made sure they were completely legally separate from commercial entities that could go bust. "In the future, museums will learn lessons."

Raising the money was now the priority, said Deuchar. Normally the Art Fund has to carefully lay out the case for why something was so important and has to be saved. "You have to put a lot of energy into establishing that fact. I would say that we have had not had to convince anyone that this collection matters … every potential donor, every observer, every critic has agreed the importance of the collection is unrivalled."

Hunt said Josiah Wedgwood was the Steve Jobs of the 18th century. "The great news is that the pottery industry in Stoke-on-Trent is putting on jobs again, it's making money again, it's exporting again. It is a growing industry and to lose the collection, which is such a source of inspiration to today's designers, would be absolutely horrific."

Public donations to the campaign will be matched pound for pound up to £500,000 by a private charitable trust. Most of the cash raised so far is from the Heritage Lottery Fund in the form of a £5m donation and also the £5.8m it gave for the museum's refurbishment in 2005.

Etruria reborn

The most breathtaking moment at the Wedgwood Museum is not, perhaps, the glorious finished pottery – though it is spectacular.

For me, it is the trays of Josiah Wedgwood's experimental firings: trays of potsherds, each incised with different numbers and letters, that represent his patient attempts to find just the right shades of chalky blue and sage green that would become his famous jasperware. It took nearly 3,000 trial firings to get there.

That and two of the four surviving "first day's vases" – beautiful, black basalt stoneware vessels shaped like Grecian vases inscribed with the date, 13 June 1769, and the motto artes Etruriae renascuntur – the arts of Etruria are reborn.

These are the pots that Wedgwood threw with his own hand, with his business partner Thomas Bentley turning the wheel, on the first operational day of their factory at Etruria – the patch of Stoke named after the region of Italy in which an enormous wealth of Attic pots had been discovered.

These objects speak eloquently of what Wedgwood represents: his powerful sense of the artistic possibilities and rich history of ceramics, combined with scientific imagination, technical skill and shrewd business acumen.

To experience the museum is to marvel at the scale of Wedgwood's achievement: from nine-year-old child worker in his brother's factory to a fellow of the Royal Society who made dinner services for the crowned heads of Europe.